Perhaps I am, but it seems to me that you don't have to be very old to remember when surround sound systems became popular in the consumer space. My dad had one installed in 1992, and that most certainly had a separate channel for the sub.

I'm not sure the age of the technology (or myself) has everything to do with this setup. It seems to me that this system was either not set up ideally, or perhaps it's a limitation of using an in-wall sub.